src/gallium/auxiliary/draw/draw_pipe_stipple.c

   1 /**************************************************************************
   2  *
   3  * Copyright 2007 Tungsten Graphics, Inc., Cedar Park, Texas.
   4  * All Rights Reserved.
   5  *
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  11  * permit persons to whom the Software is furnished to do so, subject to
  12  * the following conditions:
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  14  * The above copyright notice and this permission notice (including the
  15  * next paragraph) shall be included in all copies or substantial portions
  16  * of the Software.
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  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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  21  * IN NO EVENT SHALL TUNGSTEN GRAPHICS AND/OR ITS SUPPLIERS BE LIABLE FOR
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  26  **************************************************************************/
  27
  28 /* Authors:  Keith Whitwell <keith@tungstengraphics.com>
  29  */
  30
  31 /* Implement line stipple by cutting lines up into smaller lines.
  32  * There are hundreds of ways to implement line stipple, this is one
  33  * choice that should work in all situations, requires no state
  34  * manipulations, but with a penalty in terms of large amounts of
  35  * generated geometry.
  36  */
  37
  38
  39 #include "pipe/p_defines.h"
  40 #include "pipe/p_shader_tokens.h"
  41 #include "util/u_math.h"
  42 #include "util/u_memory.h"
  43
  44 #include "draw/draw_pipe.h"
  45
  46
  47 /** Subclass of draw_stage */
  48 struct stipple_stage {
  49    struct draw_stage stage;
  50    float counter;
  51    uint pattern;
  52    uint factor;
  53 };
  54
  55
  56 static INLINE struct stipple_stage *
  57 stipple_stage(struct draw_stage *stage)
  58 {
  59    return (struct stipple_stage *) stage;
  60 }
  61
  62
  63 /**
  64  * Compute interpolated vertex attributes for 'dst' at position 't'
  65  * between 'v0' and 'v1'.
  66  * XXX using linear interpolation for all attribs at this time.
  67  */
  68 static void
  69 screen_interp( struct draw_context *draw,
  70                struct vertex_header *dst,
  71                float t,
  72                const struct vertex_header *v0,
  73                const struct vertex_header *v1 )
  74 {
  75    uint attr;
  76    for (attr = 0; attr < draw->vs.num_vs_outputs; attr++) {
  77       const float *val0 = v0->data[attr];
  78       const float *val1 = v1->data[attr];
  79       float *newv = dst->data[attr];
  80       uint i;
  81       for (i = 0; i < 4; i++) {
  82          newv[i] = val0[i] + t * (val1[i] - val0[i]);
  83       }
  84    }
  85 }
  86
  87
  88 static void
  89 emit_segment(struct draw_stage *stage, struct prim_header *header,
  90              float t0, float t1)
  91 {
  92    struct vertex_header *v0new = dup_vert(stage, header->v[0], 0);
  93    struct vertex_header *v1new = dup_vert(stage, header->v[1], 1);
  94    struct prim_header newprim = *header;
  95
  96    if (t0 > 0.0) {
  97       screen_interp( stage->draw, v0new, t0, header->v[0], header->v[1] );
  98       newprim.v[0] = v0new;
  99    }
 100
 101    if (t1 < 1.0) {
 102       screen_interp( stage->draw, v1new, t1, header->v[0], header->v[1] );
 103       newprim.v[1] = v1new;
 104    }
 105
 106    stage->next->line( stage->next, &newprim );
 107 }
 108
 109
 110 static INLINE unsigned
 111 stipple_test(int counter, ushort pattern, int factor)
 112 {
 113    int b = (counter / factor) & 0xf;
 114    return (1 << b) & pattern;
 115 }
 116
 117
 118 static void
 119 stipple_line(struct draw_stage *stage, struct prim_header *header)
 120 {
 121    struct stipple_stage *stipple = stipple_stage(stage);
 122    struct vertex_header *v0 = header->v[0];
 123    struct vertex_header *v1 = header->v[1];
 124    const unsigned pos = stage->draw->vs.position_output;
 125    const float *pos0 = v0->data[pos];
 126    const float *pos1 = v1->data[pos];
 127    float start = 0;
 128    int state = 0;
 129
 130    float x0 = pos0[0];
 131    float x1 = pos1[0];
 132    float y0 = pos0[1];
 133    float y1 = pos1[1];
 134
 135    float dx = x0 > x1 ? x0 - x1 : x1 - x0;
 136    float dy = y0 > y1 ? y0 - y1 : y1 - y0;
 137
 138    float length = MAX2(dx, dy);
 139    int i;
 140
 141    if (header->flags & DRAW_PIPE_RESET_STIPPLE)
 142       stipple->counter = 0;
 143
 144
 145    /* XXX ToDo: intead of iterating pixel-by-pixel, use a look-up table.
 146     */
 147    for (i = 0; i < length; i++) {
 148       int result = stipple_test( (int) stipple->counter+i,
 149                                  (ushort) stipple->pattern, stipple->factor );
 150       if (result != state) {
 151          /* changing from "off" to "on" or vice versa */
 152          if (state) {
 153             if (start != i) {
 154                /* finishing an "on" segment */
 155                emit_segment( stage, header, start / length, i / length );
 156             }
 157          }
 158          else {
 159             /* starting an "on" segment */
 160             start = (float) i;
 161          }
 162          state = result;
 163       }
 164    }
 165
 166    if (state && start < length)
 167       emit_segment( stage, header, start / length, 1.0 );
 168
 169    stipple->counter += length;
 170 }
 171
 172
 173 static void
 174 reset_stipple_counter(struct draw_stage *stage)
 175 {
 176    struct stipple_stage *stipple = stipple_stage(stage);
 177    stipple->counter = 0;
 178    stage->next->reset_stipple_counter( stage->next );
 179 }
 180
 181 static void
 182 stipple_reset_point(struct draw_stage *stage, struct prim_header *header)
 183 {
 184    struct stipple_stage *stipple = stipple_stage(stage);
 185    stipple->counter = 0;
 186    stage->next->point(stage->next, header);
 187 }
 188
 189 static void
 190 stipple_reset_tri(struct draw_stage *stage, struct prim_header *header)
 191 {
 192    struct stipple_stage *stipple = stipple_stage(stage);
 193    stipple->counter = 0;
 194    stage->next->tri(stage->next, header);
 195 }
 196
 197
 198 static void
 199 stipple_first_line(struct draw_stage *stage,
 200                    struct prim_header *header)
 201 {
 202    struct stipple_stage *stipple = stipple_stage(stage);
 203    struct draw_context *draw = stage->draw;
 204
 205    stipple->pattern = draw->rasterizer->line_stipple_pattern;
 206    stipple->factor = draw->rasterizer->line_stipple_factor + 1;
 207
 208    stage->line = stipple_line;
 209    stage->line( stage, header );
 210 }
 211
 212
 213 static void
 214 stipple_flush(struct draw_stage *stage, unsigned flags)
 215 {
 216    stage->line = stipple_first_line;
 217    stage->next->flush( stage->next, flags );
 218 }
 219
 220
 221
 222
 223 static void
 224 stipple_destroy( struct draw_stage *stage )
 225 {
 226    draw_free_temp_verts( stage );
 227    FREE( stage );
 228 }
 229
 230
 231 /**
 232  * Create line stippler stage
 233  */
 234 struct draw_stage *draw_stipple_stage( struct draw_context *draw )
 235 {
 236    struct stipple_stage *stipple = CALLOC_STRUCT(stipple_stage);
 237
 238    draw_alloc_temp_verts( &stipple->stage, 2 );
 239
 240    stipple->stage.draw = draw;
 241    stipple->stage.name = "stipple";
 242    stipple->stage.next = NULL;
 243    stipple->stage.point = stipple_reset_point;
 244    stipple->stage.line = stipple_first_line;
 245    stipple->stage.tri = stipple_reset_tri;
 246    stipple->stage.reset_stipple_counter = reset_stipple_counter;
 247    stipple->stage.flush = stipple_flush;
 248    stipple->stage.destroy = stipple_destroy;
 249
 250    return &stipple->stage;
 251 }